The present invention relates to systems using digital data, and more particularly to systems for allowing asynchronous video signals to be used as inputs to a digital video system which is synchronized to a system reference signal.
In current video systems if an input video signal is not synchronous to a common reference signal, such as "house black", some kind of video frame synchronizer is required. A video frame synchronizer writes a digitized input video signal into a frame buffer memory in synchronism with the input video signal, and reads the digitized input video signal from the frame buffer memory in synchronism with the common reference signal after a suitable delay, as is well known in the art. This requires that the input video signal be synchronized with the common reference signal. However if the input video signal is asynchronous to the common reference signal, the video frame synchronizer eventually drops or repeats a video frame. This behavior is undesirable, especially if the input video signal is being recorded.